Field
Embodiments of the present disclosure provide apparatus and methods for controlling wind turbines. Particularly, embodiments of the present disclosure provide apparatus and methods for preventing power dips in wind turbines during rapid power ramping or torque ramping.
Description of the Related Art
To meet demands for stabilization in a power grid, wind turbines in the power grid are expected to provide fast changes in active power. For example, power ramping of about 10% of maximum capacity per second both upwards and downwards may be needed in active wind power platforms. However, as ramping rate requirement in power grids increases, power dips may occur during rapid power ramping causing instability problems in the power grid.
FIG. 1 is a schematic graph showing power dips following rapid power ramping with large ramp amplitude under extreme circumstances. The x-axis of FIG. 1 denotes time in seconds and the y-axis denotes the normalized power output in p.u. (per unit) of a wind turbine. Curve 102 represents a schematic power output—time graph associated with a 0.4 p.u. power ramping at a rate of about 0.1 p.u. per second. The curve 102 has a dip 104 after a ramping period starts at 400 seconds. The dip 104 indicates a dip in power output of the wind turbine after the ramping period. Curve 106 is a power output—time graph associated with a 0.3 p.u. power ramping at a rate of about 0.1 p.u. per second. The curve 106 has a dip 108 after the ramping period. The dip 108 indicates a dip in power output of the wind turbine after the ramping period. As illustrated in FIG. 1, power dips may occur after rapid power ramping causes instability in the power grid. The observed power dip is an inherent problem of conventional wind turbine controllers.
Therefore, there is need for apparatus and methods to improve power output stability after power ramping in wind turbines.